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Libbrecht, S., E. Osquiguil, B. Wuyts, M. Maenhoudt, Z. X. Gao, and Y. Bruynseraede. "Effect of room temperature annealing on the properties of oxygen- deficient YBa2Cu3Ox films." Physica C: Superconductivity and its applications 206, no. 1-2 (1993): 51–58.
Abstract: Annealing at room temperature of quenched oxygen-depleted YBa2Cu3Oxn (6.5?xn<6.8) films, produces a clear increase in the critical temperature Tc and current density Jc, while the normal state resistivity ?{variant}xx and Hall coefficient RH decrease as a function of annealing time, indicating an increase in carrier density. The enhancement of the critical current density Jc is more pronounced at high fields and temperatures due to a shift of the irreversibility line, which scales with the increasing Tc. The observed changes are accompanied by corresponding changes in the crystalline structure, which can be related to oxygen ordering effects.
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Osquiguil, E., M. Maenhoudt, B. Wuyts, Y. Bruynseraede, D. Lederman, and I. K. Schuller. "Photoexcitation and oxygen ordering in YBa2Cu3Ox films." Physical Review B 49, no. 5 (1994): 3675–3678.
Abstract: We report on the photoinduced enhancement of the critical temperature ?Tc and the in-plane conductivity ??ab measured in a c-axis-oriented YBa2Cu3Ox film as a function of oxygen concentration (6.4?x?7). Both ?Tc and ??ab decrease with the oxygen content, display a plateaulike behavior for 6.6?x?6.75, and become zero at x=7. This dependence of ?Tc on x is similar to that observed for the Tc enhancement due to ordering effects in oxygen-deficient YBa2Cu3Ox single crystals. We propose that the persistent photoinduced changes in YBa2Cu3Ox films are due to photoassisted oxygen ordering.
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Martin, J. I., B. Wuyts, M. Maenhoudt, E. Osquiguil, J. L. Vicent, V. V. Moshchalkov, and Y. Bruynseraede. "Sign reversal of the flux flow Hall effect in oxygen deficient YBa2Cu3Ox films." Physica C: Superconductivity and its applications 235-240, no. PART 2 (1994): 1451–1452.
Abstract: The Hall effect of high temperature superconductors has been reported to slow in some cases a striking sign reversal near Tc, the origin of which is not yet fully understood. We report on measurements of the Hall effect in the mixed state of oxygen deficient YBa2Cu3Ox thin films, for 7?
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Libbrecht, S., A. J. J. van Dalen, B. Wuyts, M. Maenhoudt, Z. X. Gao, E. Osquiguil, R. Griessen, and Y. Bruynseraede. "Magnetic properties of oxygen deficient Yba2Cu3Ox thin films." Physica C: Superconductivity and its applications 235-240, no. PART 5 (1994): 2889–2890.
Abstract: We have invesitgated several superconducting properties of oxygen defiecient YBa2Cu3Ox thin films, with oxygen contents ranging from x = 6.55 to x = 7. By means of torque magnetometry, the temperature dependence of the superconducting current dendity js and relaxation rate of the magnetization Q is measured in an (almost perpendicular) applied magnetic induction of 0.6 T. As the oxygen content is reduced, js decreases, whereas Q increases. Both properties are influenced by the decreased dpoing level as well as the enhanced anisotropy of oxygen depleted YBa2Cu3Ox. Using the Generalixed Inversion Scheme derived by Schnak et al. we obtain the current dependence of the activation energy U(f). We show that U(j) is lowered when the oxygen content is reduced.
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Wuyts, B., M. Maenhoudt, S. Libbrecht, Z. X. Gao, E. Osquiguil, V. V. Moshchalkov, and Y. Bruynseraede. "Linear relation between the Hall angle slope and the carrier density in YBa2Cu3Ox films." Physica C: Superconductivity and its applications 235-240, no. PART 2 (1994): 1369–1370.
Abstract: A universal relation cot?H??{variant}/RHB = ?T2 + C for the Hall angle ?H has been experimentally observed served in a wide variety of high-Tc systems. In contrast to the linear temperature dependence of the resistivity ?{variant} or the inverse Hall coefficient R-1H, the T2-dependence of cot?H remains valid in under- and overdoped systems. We present a systematic study of cot?H(T) in oxygen deficient epitaxial YBa2Cu3Ox thin films. We find evidence for a linear relation between ?, the slope of cot?H versus T2, and the carrier concentration. Moreover, we find a steep increase in the intercept C = cot?H (T = 0) below x ? 6.6.
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Wuyts, B., E. Osquiguil, M. Maenhoudt, S. Libbrecht, Z. X. Gao, and Y. Bruynseraede. "Relation between the Hall angle slope and the carrier density in oxygen-depleted YBa2Cu3Ox films." Physica C: Superconductivity and its applications 222, no. 3-4 (1994): 341–348.
Abstract: A detailed study of the Hall angle cot?H in YBa2Cu3Ox epitaxial thin films with various oxygen contents clearly shows the existence of a linear relation between the slope of cot?H versus T2 and the carrier density. The zero-temperature intercept C=cot?H(T=0 K) and the mobility at room temperature change substantially for an oxygen content x?6.6, indicating that both effects are closely related.
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Bruynseraede, Y., E. Osquiguil, M. Maenhoudt, B. Wuyts, G. Nieva, J. Guimpel, D. Lederman, and I. K. Schuller. "Enhancement of Superconductivity by Photoexcitation." The Vortex State (NATO Science Series C: Mathematical and Physical Sciences) 438 (1994): 303–312.
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